PT woes..... 1850 wiring

   / PT woes..... 1850 wiring #1  


Silver Member
Mar 30, 2011
John Deere 430 PT-1850 JD 3520 Komatsu 35MR
So, the 1850 and I haven't really been getting along lately. Every time I go mowing, something goes wrong.

I attribute a lot of it to "working out the kinks," but today's escapades have left me a little defeated.

Last time I mowed, it was very hot out. I saw high engine temps (220F+) after about 20 mins and the hydraulic oil cooler fan never came on. This afternoon, I removed the engine cooling shroud and it was mostly clean. I found a wire off of the temp sensor in the bottom of the engine bay, so I replaced the connector and reattached it. I went out to get the temp up and do some mowing to see what happened.

On the first pass across the hill, the seat tipped fully to the left, even though I was only on a ~20* slope. Limped it back home with one foot on the treadle and the other on the seat switch while kind of hanging off of the canopy. It was "fun."

Current Situation:

Its further become clear that I have some electrical gremlins (fan, beacon and rear work light do not work either) and I'm sure that my seat control problem is in there too, but I honestly don't even know where to look. I haven't had a chance to put a meter on it or anything, so that will likely tell me more. PT very kindly sent me a "Parts Manual" with some other basic info, but I have nothing on the electrical system or even where to find fuse boxes or anything.

I'd appreciate any pointers. Thanks!

Edit: In the good news dept. I traded 2 cases of beer for a pre-MM 9' fisher plow in decent shape with a new cutting edge. An afternoon of welding and some new hoses and we should have a snow solution!
   / PT woes..... 1850 wiring #2  
Well, at least you got a good deal at the end there... :thumbsup:

I think there's a recent thread with a wiring diagram for your machine, and a re-done wiring diagram, too, as I recall. Hopefully someone will chime in on it today.
   / PT woes..... 1850 wiring #3  
I also added "1850 wiring" to the end of your thread title, if you don't mind. It may get more responses that way.
   / PT woes..... 1850 wiring #4  
Whenever I see multiple circuits having trouble, I think of poor grounding as a likely cause.
I think that your fuse box is under the muffler-ish, on the inside of the tub wall.
The other “easy place” to look is by removing the panel on the front side of the dashboard, I.e. not the dashboard, but the plain metal plate toward the front arms.
For the seat, try looking under the seat for the mercury switch, and check the connections there, and on the solenoid inside the engine tub.

I have upgraded many of my wires to marine grade wires, and I use crimp fittings that have low temp solder in them, along with a low temperature adhesive that melts when you heat shrink them on. (Del City, and West Marine). It is probably overkill, but I hate fixing things more than once.

All the best, Peter
I would start by clamping a jumper cable from the front to the battery ground, and from the battery ground to the engine mounting bolt.
   / PT woes..... 1850 wiring #5  
On the right side of the engine compartment, there are multiple spade electrical connections including ones for the seat and the cooling fan. If you are not careful, it is easy to knock those off. Replacing them is a long wished for mod that I never find time for.

And as Peter said, a common problem is bad grounds.

   / PT woes..... 1850 wiring #6  
As Ken said, Right hand side and in front of the gas tank is where the solenoid for the seat is for my machine. It sounds like a short / disconnect but it could be a blown cylinder. start with electrical, make sure the connections are solid, then move forward.

On the engine cooler shroud, are you talking the top piece or are you talking the side panel?

At 6K for the machine you have a deal. While you are going to need to iron out the kinks it is worth the effort Don't get down (I know I did but now it is all just part of equipment ownership)
   / PT woes..... 1850 wiring #7  
On my 1845 the mercury switches for the tilt seat are in a metal box mounted on the back of the seat. The operator presence switch in the bottom of the seat is connected through this box and I was able to reduce voltage drop in the starting circuit by soldering the connections for the operator presence switch.
My seat often ends up tilted like your picture but straightens up when the tractor is started. My seat doesn't have the power to maintain level on steep slopes unless I am careful about how I sit in the seat. I asked Terry years ago about this and he basically told me that the hydraulic cylinder for the tilt seat has limited power and that what I was experiencing was normal.
   / PT woes..... 1850 wiring
  • Thread Starter
Thanks for changing the title, it seems to have helped!

I am certain that it is not a problem with the hydraulic cylinder. As it bleeds down when parked, the seat starts to move toward neutral, when I start the tractor, the seat will quickly move back to the left. As far as hydraulic power to the seat, the only problem that I've had is too much power, sometimes it gets violent!

I hope to get some time to work on it tonight, but I'll start with fuses, grounds, and connections and go from there.

Thanks guys, I'll let you know how I make out!
   / PT woes..... 1850 wiring #9  
Your seat issue really sounds like one of the spade connectors came off of the solenoids on the side of the tub or they got swapped.

I did have a weird problem one time but I can not remember for sure what it was. It was something like the adjustable pressure relief for the draft control valve was stuck, something I would have thought was totally unrelated.

   / PT woes..... 1850 wiring #10  
I agree with Ken. I would also check the merc switches behind the seat. Just FYI my seat wire rubbed and was exposed. You had to run new wires. If you do use high quality boat wire